Problems with Shellac

[IronWood]

I recently finished a dresser/changing table for my new son's room and sealed the top with about 10 coats of Shellac (I'm a sucker for the super glossy look) but when I started putting items on it, they left a mark! At first I thought it was because they were too heavy (lamps) but then a small foam pad for changing left the same "ripples".

Have any of you had this happen or know what could have caused it?

I let each coat cure at least 2-4 hours (some coats longer) and the final coat didn't see use for 2 weeks.

Are the coats too thick? Not cured enough? It's sad because I loved the ease of application but won't use Shellac anymore because of the final result, I'm just glad it was on one of my pieces and not something for a client!

Any insight would be much appreciated.

[AceHoleInOne]

Provided your shellac is fresh and doing that many coats. Yes the shellac probably needs more time to gas off and fully cure. Additionally, porous woods will take longer to gas off due to the wood pulling in solvent and then having to release back out. I know finishes seem dry to the touch. However, they may not be fully cured, so based on drying conditions, how many coats, etc...could very well take more than 2 weeks to fully cure! 10 coats is pretty thick.

The only finishes I know that can fully cure in just a few days are those forced cured with heat or UV.

-Ace-

[IronWood]

Thanks for the advice. So should I lay thinner coats and let each coat dry overnight or longer? Should I not use that many coats?

[dwacker]

Thick shellac is shellac destined to fail. 10 Coats is a bunch of shellac unless you're french polishing. How was the finish applied? What cut did you use?

Don

[IronWood]

I used a 2lb cut appplied with a high quality brush...ya know, now that I tye it, I can see how that could have been way too thick, Ha!

[dwacker]

With shellac its easiest to throw everything you've learned about finishing with modern finishes out the window. If your going for that sweet highly polished shellac look then padding is really the best way to go. Many , many very thin coats and I use the term coats loosely. Not really coats but more re wetting. The end result is still a super thin but highly polished finish. Look up french polishing on the web, there may be some videos around.

Don

[Mark Reuten]

One interesting characteristic of shellac is that it levels itself out over an extended length of time. I had a stringed instrument I built last winter with a french polish finish. I wasn't all that happy with my results as there was a certain amount of swirl marks that would not go away despite my best efforts. I went away on an extended trip of a bout two months. Upon my return i was surprised to see that the swirls had levelled out and disappeared. I had read about shellac requiring some time to shrink up but I wasn't aware of just how much time was required and how much it would change.

It is one of those finishes that is both challenging to the uninitiated and simple to the experienced yet seems to require a touch of luck and magic thrown in just the same.

Don't give up on using it as it has a lot of wonderful applications.